Oak's Parcel prevented progress glitch

Please note that this glitch only exists in the Japanese versions of the game, or is otherwise a glitch from a Pokémon game which was only released in Japan.

The never recieve the Pokédex glitch or sometimes the prevented progress glitch is one which only exists within Pokémon Green and the Japanese version of Pokémon Red. When performed, the player will no longer be able to recieve the Pokédex therefore he or she is unable to complete the game without starting a new save file or performing a glitch. This glitch was fixed in the translated versions of Pokémon Red and is not present in Pokémon Blue and Pokémon Yellow.

Method

1. The player must start a new game and continue as normal until he or she recieves Oak's Parcel.
2. Before delivering Oak's Parcel the player must evolve his or her starter Pokémon, so that he or she would have owned two or more Pokémon.
3. When attempting to deliver Oak's Parcel the game will presume that the player has already delivered it, therefore he or she will never be able to obtain any Pokéballs or proceed past the Old Man.

Explanation

For the byte which manages whether Professor Oak will give the player or Pokédex or not Nintendo decided that it would be turned to the variable 01 (no) if the player has seen two or more Pokémon. Typically the player would only own two or more Pokémon if he or she caught another Pokémon with a Pokéball, so for this reason Nintendo would make it so that the player could only obtain Pokéballs after he or she obtains the Pokédex. However, evolution still adds an extra value to the amount of owned Pokémon regardless.